Is it worth it to purchase a 14b turbo and install ki?

[96gstdsm]

Well i have been looking into getting a new turbo. I plan to get the evo3 16g turbo in the future. I don't feel like spending that much money yet, as i don't know if i will have this car for a long time or not. I love the car but the fwd thing is a bit annoying. But anyways, my question here is, is it worth it for performance to buy a used 14b turbo for around $100 and also a 2g install kit. Would i see nice gains over stock t-25 power and stock fuel system? I would plan to run the 14b around 15 or 16 hopefully. I know bench racing is not allowed on here, but i am just curious as to what sort of gains you are able to get with just swapping over to the 14b before i purchase it. Whats the highest psi i could run while still using the stock fuel setup? Would i get much better top end?
Any input i would really appreciate. I figure if there are nice gains it would be a nice temporary swap.
---Ryan.

 

[RedTurboEclipse]

At what psi would I need to replace the headgasket considering it is in good shape now? And arp headstuds I was told I would not need untill I had like over 400hp! Is that not true? If i'm running 15 psi or even like 18 i wouldn't need head gasket would I? Or head studs? Over 15 psi i would need to upgrade my fuel and all though correct?

I just mentioned this a few posts above ^^^^^^^

If you want other testimonials, do a search for head gasket, and you will see some threads on people questioning how much boost stock HG can handle. I have seen a regular 25lbs. I have ran as much as that myself.

 

[96gstdsm]

I just mentioned this a few posts above ^^^^^^^

If you want other testimonials, do a search for head gasket, and you will see some threads on people questioning how much boost stock HG can handle. I have seen a regular 25lbs. I have ran as much as that myself.

Ok thanks. So running like 15 or so i shouldn't have to worry about the head gasket being a problem, unless it was already in bad shape? Obviously things can happen but for that sort of psi it should be able to handle that i would think. And what about the head studs someone suggested? I was under the impression that you only needed those with real high horsepower set ups. Is this not correct?

 

[RedTurboEclipse]

Well when your up to the mods such as cams, and you are in the vicinity, you might as well. Usually thats the case, and usually with cams, the setup is almost always up in HP.

 

[calreef18]

What psi was the t-25 at and what psi was the 14b at?

Both at 15psi. Also forgot that I added a straight megan downpipe with the 14b install, but still have the stock post cat piping and muffler.

 

[Blackmitzu]

Guessing 3200 lbs for you and your car @ 12.8s quarter mile = 356 hp at the crank. Assuming 11 AFR and BFSC of 0.55:

Wa = 35.9 lb/min = 0.214 m^3/s
Boost = 20 psi ~=34.7 psi absolute
Pressure ratio = 34.7/13.7 = 2.5

Looking at the chart, you were at ~65% VE border for the 14b and nearing the choke line but not past it. You could have taken it a little further still, but only seen marginal gains if any due to droping into the 60% VE

I probably could have pushed it a little bit farther, but hey i was satisfied from the results i had, considering at the time i still had the stock turbo and was running twelves.

 

[Blackmitzu]

High boost as in 25+ PSI? As there are several posts and claims/logs from owners who have ran 24 just fine, myself included. Or did you mean to say high boost safely without worrying.

Yes that is exactly what i meant. "Better safe than sorry"

 

[Blackmitzu]

Ok thanks. So running like 15 or so i shouldn't have to worry about the head gasket being a problem, unless it was already in bad shape? Obviously things can happen but for that sort of psi it should be able to handle that i would think. And what about the head studs someone suggested? I was under the impression that you only needed those with real high horsepower set ups. Is this not correct?

Most vendors offer a combo(metal head gasket and arp head studs) when purchasing a metal head gasket, that is what i bought and also why i recomended doing both of them at the same time.

 

[96gstdsm]

Ok well i still have to decide which route to go with. Just installed my mbc today on my t-25 and i really noticed big gains from stock boost. I doubt the numbers are much crazier but it feels a hell of a lot faster and pulls to higher rpm's too. I am definately very happy with it at the moment but i'm sure i'll get used to it real soon and then need to upgrade again .

One question regarding this. Is it dangerous to be driving it without a logger with the boost put up? I have a boost gauge of course but no logger as of yet.

 

[calreef18]

It can be dicey due to not knowing if timing is being pulled, but fwiw about 14-15psi roughly will be ok on the stock fuel system. If you can do the fuel pump rewire that can give you some headroom as well. Get a logger if you can, otherwise, if it were my car I'd keep it around 12-13 to be safe.

 

[96gstdsm]

It can be dicey due to not knowing if timing is being pulled, but fwiw about 14-15psi roughly will be ok on the stock fuel system. If you can do the fuel pump rewire that can give you some headroom as well. Get a logger if you can, otherwise, if it were my car I'd keep it around 12-13 to be safe.

I think i will just buy a datalogger of some sort to be safe.
I have another question for you or anyone else who might know.
The psi seems to change depending on the gear i am in. Is this normal? It seems hard to get the psi up much at all in 1st gear, although it does feel fast still. Then in 2nd it seems to go to around 10 but will then shoot up to like 14 or so and then in 3rd went to about 16 and then in 5th seemed to go to like 18 if i stepped on it real hard. I of course only did this once in 5th as to not damage anything. I turned the boost down a little and it seems to be normally around 15 or so. Is that normal with the t-25? The only mods i have regarding the turbo and all is an intake and a 1g bov. Can you get boost spike from installing a mbc?
The overall normal boost is around 15 or so though.

 

[Blackmitzu]

Boost spike usually happens when running higher boost levels.

 

[Splitpi]

It can be dicey due to not knowing if timing is being pulled, but fwiw about 14-15psi roughly will be ok on the stock fuel system. If you can do the fuel pump rewire that can give you some headroom as well. Get a logger if you can, otherwise, if it were my car I'd keep it around 12-13 to be safe.

With Stock 450 cc injectors, BSFC 0.55 and 80% duty cycle max theoretical HP is:

((450/10.5)*4*.80)/0.55 = 249 hp at the crank
550 cc inj = 257 hp
650 cc inj = 304 hp

The stock fuel pump will handle this. According to RRE the stock maxes out at: 2160 cc/min (or enough to fuel four 540 cc/min injectors) and the rewired maxes out at: 2607 cc/min (or enough to fuel four 651 cc/min injectors).

http://www.roadraceengineering.com/fuelpumpflowrates.htm

I should note injectors are usually manufactored rated for 80% duty cycle.

Now to get the air flow from the HP.

249*0.1008 = 25.1 lb/min
257*0.1008 = 25.9 lb/min
304*0.1008 = 30.6 lb/min

So choose either the psi (in pressure ratio) you want to run or the efficiency and crossreference the air flow rate to find either the pressure ratio of efficiency depending on what you are searching for on the turbo map. With the efficiency (verified by pressure ration correlated to air flow) you can calculate roughly at what RPM range that will be achieved at.

Example: 25.1 lb/min = 0.15 m^3/2
Following 0.15 m^3/s flow rate on the chart up I see an ideal VE of 74% at 1.9 pressure ratio. This is truely the best VE you can achieve at that blow rate and having the lowest psi.
http://not2fast.wryday.com/turbo/maps/td05-14b.gif

1.9 pressure ratio ~= (x+14.7-1)/(14.7-1) = 12.33 psi at sea level and assuming 1 psi drop from pre-turbo and another psi drop post turbo to manifold.

RPM = (2*25.1*639.6*(460+90))/((12.33+13.7)*0.74*122.04)=7375 rpms

However if increased psi to max of 74% VE (PE = 2.2 = 16.44 psi) RPMs then equals 6300 RPMs.

Does this make sense?

Comments:
What I am trying to show is that I can make the same horsepower at different psi's, so psi is not means from which to measure a turbo. And since by my understandings, engine power is actually what causes HG failure rather than psi we need to be talking in different terms which is CFM and when in RPMs you want that power to occur.

Like if I say my car runs a 90 mph, it is rather meaningless to say it like that. Since you don't know if I am talking in terms of 1/4 miles, 1 mile or 1 million miles or even in how many seconds it took to achieve 90 mph. However if I say either "a 90 mph 1/4 mile" or "90 mph in 14 seconds" now we have a tangible value as we have velocity and either distance or time. The same is true for turbos. We nee psi & we need either the Efficiency or Air flow to truely make it a tangible value of the turbo.